Magnetic disk systems based on perpendicular magnetic recording are increasingly employed. In such a magnetic disk system based on perpendicular magnetic recording, a magnetic disk having a magnetic recording layer under which a soft magnetic underlayer is formed and a single-pole type magnetic head including a main pole having a pole face facing the magnetic disk and an auxiliary pole are used.
The main pole of such magnetic head has the fore-end portion of a long thin extension toward the pole face. Because the length of this fore-end portion affects the properties of a magnetic field for recording, it is required to lap the pole face with a high accuracy. For this purpose, alignment marks may be provided and a method of lapping the pole face, while detecting the amount of lapping work may be used.